TEHRAN, Iran (CNN) --Dozens of Iranian legislators held a second day of protests in the halls of parliament Monday, walking out of a session and holding a sit-in to object to a hard-line commission's disqualification of moderate election candidates, according to the state-run news agency, IRNA.

A number of sitting members of parliament were included in the Guardian Council's ban on hundreds of candidates in the February 20 election -- all allied with moderate reformist President Mohammad Khatami, the agency said.

About 80 deputies from the 290-seat parliament joined the sit-in Monday, 10 more than began the protest on Sunday.

Reformers have made steady inroads in the Iranian electoral process since the 1979 Islamic Revolution, pledging to relax the hard-line ayatollahs' iron grip on Iranian society.

The head of parliament's national security and foreign policy commission, Mohsen Mirdamadi -- who was rejected by the council -- described the rejections as "a civilian coup d'etat," IRNA said.

"They have barred certain individuals in every electoral constituency in order to clear the way for their favorite candidates," he said. "By doing so, they have practically specified the make-up of the seventh parliament from now, and this is not an election, but a selection."

The U.S. State Department is siding with the protesters and calling on the Iranian government to reverse the commission's decision.

"We, as a matter of course, support free and fair elections in Iran," said State Department deputy spokesman Adam Ereli. "And we are therefore opposed to interference in the electoral process."

At the Haydarnia sports gym in Tehran -- where disqualified candidates were told they could appeal the council's ruling -- several banned candidates held a sit-in when the gym's doors remained locked and representatives of the Guardian Council failed to show.

The president's younger brother, Mohammad Reza Khatami -- head of the country's largest reform party, the Islamic Iran Participation Front -- was among the disqualified candidates.

Khatami speaks to journalists Sunday after a Cabinet meeting in Tehran.

"The reason for the rejections as well as any thing behind the scene is crystal clear to us," Khatami told reporters.

"The sit-in today is the beginning of a movement which will have more ramifications, and if the legitimate demands of the MPs (members of parliament) are not addressed, it will become more widespread and take up other dimensions," he said.

The president appealed for calm.

"Any action which may create tensions must be avoided and instead ways which help the protests bear fruit must be explored," President Mohammad Khatami said after a Cabinet session, but he said the electoral board's rejection of prominent figures "makes no sense."

"If the reason for their disqualification has been proved, (the board) must present evidence and reasons," he said.

Ereli said "decisions about who should govern a country are best made by the citizens of that nation through an open and transparent process.

"The options of the people in that regard shouldn't be limited by other institutions so as to prejudge the election or the outcome of an election," he said.

Although the Guardian Council has the power to ban candidates, Ereli noted that "there are measures within the government and within governmental processes for the government of Iran to invalidate those decisions."

Calling the government's handling of the electoral process "one of the fundamental measurements of its credibility," Ereli called on the Iranian government "to disavow attempts by the Guardian Council to shape the outcome of the February 20 parliamentary elections."

"It's important that the voice of the people be heard in Iran," he said.

Although the Guardian Council is selected by Iranian Supreme Leader Ayatollah Ali Khamenei, the president said he believes the disqualifications contradict the ayatollah's view.

Pledging to follow "legal channels to deal with this issue," Khatami added that "we must always be worried about the public dissatisfaction and God willing, the Guardian Council will make amends."

Exactly how many of the 8,200 hopefuls for February's legislative elections have been barred remains unclear. However, initial results from several provinces carried by the official IRNA news agency indicated it was between 50 percent and 60 percent, Reuters reported.

Parliament members say about 900 of the 1,700 hopefuls for seats in Tehran have also been disqualified from running.